Liquid crystal display device

ABSTRACT

A liquid crystal display device includes a liquid crystal cell including a liquid crystal layer twist-aligned at 90° sandwiched between a pair of substrates, first and second polarizing layers arranged to sandwich the liquid crystal cell therebetween so that their absorption axes set to parallel with directions crossing aligning treatment directions of the substrates at 45°, and viewing angle compensating plates respectively arranged between the polarizing layers and the liquid crystal cell. A total value of retardations in a thickness direction, defined as a value of a product of a phase difference within a plane perpendicular to substrate surfaces of the liquid crystal cell and a layer thickness, of optical layers present between the polarizing layers is set to a value that substantially cancels out a retardation in a liquid crystal layer thickness direction when a saturation voltage is applied to the liquid crystal layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of U.S.application Ser. No. 11/804,950 filed May 21, 2007 now U.S. Pat. No.7,532,288, which is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2007-016655, filed Jan. 26, 2007,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a TN (twisted nematic) type liquidcrystal display device.

2. Description of the Related Art

As a TN type liquid crystal display device, there is known a liquidcrystal display device that includes a liquid crystal cell including aliquid crystal layer in which liquid crystal molecules are twist-alignedat a twisted angle of substantially 90° between a pair of substrates,and a pair of polarizing plates arranged to sandwich this liquid crystalcell therebetween, wherein one of the pair of polarizing plates isarranged in such a direction that an absorption axis sets to parallelwith a direction crossing an aligning treatment direction of onesubstrate of the liquid crystal cell at 45° {see JP-A 2006-285220(KOKAI)}.

This liquid crystal display device enhances contrast and improvesgrayscale inversion in an intermediate gradation. Further, in thisliquid crystal display device, viewing angle compensating plates arerespectively arranged between the liquid crystal cell and the pair ofpolarizing plates, and arranging a retardation plate improves viewingangle characteristics.

However, the TN type liquid crystal display device does not sufficientlycompensate viewing angle dependency of a transmittance, and hencesufficiently wide viewing angle characteristics does not be obtained.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provideda liquid crystal display device comprising:

a liquid crystal cell Including a pair of substrates in which at leastone electrode and an alignment film that covers the electrode areprovided on each of inner surfaces of the substrates facing each other,and a liquid crystal layer that is sandwiched between the substrates andIncludes liquid crystal molecules twist-aligned at substantially 90°;

first and second polarizing plates that are arranged on both sides ofthe liquid crystal cell, each of the polarizing plates including apolarizing layer having a transmission axis allowing transmission oflinear polarized light and an absorption axis in a directionperpendicular to the transmission axis, and at least one base film thatsupports the polarizing layer; and

first and second viewing angle compensating layers that are respectivelyarranged between the liquid crystal cell and the first and secondpolarizing plates, each of the viewing angle compensating layers havinga phase difference within a plane parallel to substrate surfaces of theliquid crystal cell and a phase difference within a plane perpendicularto the substrate surfaces,

wherein a total value of retardations in a thickness direction, each ofwhich is a product of a phase difference within a plane perpendicular tothe substrate surfaces and a layer thickness, of a plurality of opticallayers between the first and second polarizing layers, including atleast the first and second viewing angle compensating layers butexcluding the liquid crystal layer, is set to a value that cancels out aretardation in a liquid crystal layer thickness direction, which is aproduct of a phase difference within a plane perpendicular to thesubstrate surfaces and a liquid crystal layer thickness, of the liquidcrystal layer when a voltage sufficiently high to raise and align theliquid crystal molecules with respect to the substrate surfaces isapplied to the liquid crystal layer between the electrodes of the firstand second substrates.

Furthermore, according to a second aspect of the present invention,there is provided a liquid crystal display device comprising:

a first substrate in which at least one electrode and a first alignmentfilm that covers the first electrode and is subjected to an aligningtreatment in a predetermined first direction are provided on one surfacethereof;

a second substrate that is arranged to face an electrode formationsurface of the first electrode, and in which at least one secondelectrode facing the first electrode and a second alignment film thatcovers the second electrode and is subjected to an aligning treatment ina second direction crossing the first direction at an angle ofsubstantially 90° are provided on a surface facing the first substrate;

a liquid crystal layer that is sandwiched between the first alignmentfilm of the first substrate and the second alignment film of the secondsubstrate and includes liquid crystal molecules twist-aligned betweenthe first alignment film and the second alignment film at a twistedangle of substantially 90°;

a first polarizing plate that includes a first polarizing layer that isarranged to face an outer surface opposite to an electrode formationsurface of the first substrate and has an absorption axis in a directioncrossing an aligning treatment direction of the first alignment film atan angle of substantially 45°, and a base film formed of a resin filmthat is provided on a surface of the first polarizing layer facing atleast the first substrate and has a retardation in a thicknessdirection, which is a product of a phase difference within a planeperpendicular to substrate surfaces of the first and second substratesand a layer thickness;

a second polarizing plate that includes a second polarizing layer thatis arranged to face an outer surface opposite to an electrode formationsurface of the second substrate and has an absorption axis in adirection substantially perpendicular to or substantially parallel tothe absorption axis of the first polarizing layer, and a base filmformed of a resin film that is provided on a surface of the secondpolarizing layer facing at least the second substrate and has aretardation in the thickness direction, which is a product of a phasedifference within a plane perpendicular to the substrate surfaces and alayer thickness; and

first and second viewing angle compensating plates that are respectivelyarranged between the first substrate and the first polarizing plate andbetween the second substrate and the second polarizing plate, eachviewing angle compensating plate including a viewing angle compensatinglayer having a phase difference within a plane parallel to the substratesurfaces and a phase difference within a plane perpendicular to thesubstrate surfaces, and a base film formed of a resin film that isprovided on at least one surface of the viewing angle compensating layerand has a retardation in the thickness direction, which is a product ofa phase difference within a plane perpendicular to the substratesurfaces and a layer thickness,

wherein a total value of the retardation values in the thicknessdirection, each of which is a product of a phase difference within aplane perpendicular to the substrate surfaces and a layer thickness, ofa plurality of optical layers between the first polarizing layer of thefirst polarizing plate and the second polarizing layer of the secondpolarizing plate, including at least the base films on the surfaces ofthe first and second polarizing plates facing the first and secondsubstrates, the respective viewing angle compensating layers of thefirst and second viewing angle compensating plates, and the base filmsof the first and second viewing angle compensating plates but excludingthe liquid crystal layer, and a retardation value in the liquid crystallayer thickness direction, which is a product of a phase differencewithin a plate perpendicular to the substrate surfaces and a liquidcrystal layer thickness, of the liquid crystal layer when a voltagesufficiently high to raise and align the liquid crystal molecules withrespect to the substrate surfaces is applied to the liquid crystal layerbetween the electrodes of the first and second substrates is set to therange of −80 nm to +80 nm.

Moreover, according to a third aspect of the present invention, there isprovided a liquid crystal display device comprising:

a first substrate in which at least one electrode and a first alignmentfilm that covers the first electrode and is subjected to an aligningtreatment in a predetermined first direction are provided on one surfacethereof;

a second substrate that is arranged to face an electrode formationsurface of the first substrate, and in which at least one secondelectrode that faces the first electrode and a second alignment filmthat covers the second electrode and is subjected to an aligningtreatment in a second direction crossing the first direction at an angleof substantially 90° are provided on a surface facing the firstsubstrate;

a liquid crystal layer that is sandwiched between the first alignmentfilm of the first substrate and the second alignment film of the secondsubstrate and includes liquid crystal molecules twist-aligned betweenthe first alignment film and the second alignment film at a twistedangle of substantially 90°;

a first polarizing layer that is arranged to face an outer surfaceopposite to the electrode formation surface of the first substrate andhas an absorption axis in a direction crossing an aligning treatmentdirection of the first alignment film at an angle of substantially 45′;

a second polarizing layer that is arranged to face an outer surfaceopposite to an electrode formation surface of the second substrate andhas an absorption axis in a direction substantially perpendicular to orsubstantially parallel to the absorption axis of the first polarizinglayer; and

first and second viewing angle compensating layers that are respectivelyarranged between the first substrate and the first polarizing layer andbetween the second substrate and the second polarizing layer, eachviewing angle compensating layer having a phase difference within aplane parallel to substrate surfaces of the first and second substratesand a phase difference within a plane perpendicular to the substratesurfaces,

wherein, in regard to a plurality of optical layers between the firstand second polarizing layers including at least the first and secondviewing angle compensating layers but excluding the liquid crystallayer, a retardation Rth in a thickness direction is set to the rangesatisfying the following expression:−80 nm<Rth−0.83Δnd<80 nmwhere one and the other of two directions perpendicular to each otherwithin a plane parallel to the substrate surfaces are an X axis and a Yaxis, a thickness direction perpendicular to the substrate surfaces is aZ axis, nx is a refractive index in the X axis direction, ny is arefractive index in the Y axis direction, nz is a refractive index inthe Z axis direction, d is a layer thickness of the optical layer, Rthiis a retardation in the thickness direction of each optical layerrepresented as {(nx+ny)/2−nz}·d, Rth is the retardation in the thicknessdirection obtained by adding values of the retardations Rthi in thethickness direction of the respective optical layers, and Δnd is aproduct of an anisotropic refractive index Δn of a liquid crystalmaterial constituting the liquid crystal layer and a liquid crystalthickness d.

Advantages of the invention will be set forth in the description whichfollows, and in part will be obvious from the description, or may belearned by practice of the invention. Advantages of the invention may berealized and obtained by means of the instrumentalities and combinationsparticularly pointed out hereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 is a schematic cross-sectional view of a liquid crystal displaydevice showing a first embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view of a part of a liquid crystalcell;

FIG. 3 is an enlarged cross-sectional view of a part of a viewing anglecompensating plate;

FIG. 4 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, and directions of optical axes of first andsecond viewing angle compensating layers in the first embodiment;

FIG. 5 is a view showing a relationship between a ratio of liquidcrystal layer thicknesses d_(R), d_(G), and d_(B) of pixel portions ofrespective colors, i.e., red, green, and blue and a display chromaticitywhen white is displayed in the liquid crystal display device accordingto the first embodiment;

FIG. 6 is a view showing a relationship between Δnd of a liquid crystallayer and a retardation Rth_(LC) in a thickness direction of the liquidcrystal layer when a saturation voltage is applied in the liquid crystaldisplay device according to the first embodiment;

FIG. 7 is a view showing a relationship between an in-plane retardationRo, Δnd of the liquid crystal layer, and a transmittance, the in-planeretardation Ro being obtained by adding respective in-plane retardationvalues of base films of a plurality of optical layers between the firstand second polarizing layers excluding the liquid crystal layer in theliquid crystal display device according to the first embodiment;

FIGS. 8A to 8D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the first embodiment;

FIGS. 9A to 9D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% gradation of white display) display T₂₀ in the liquidcrystal display device according to a modification of the firstembodiment;

FIG. 10 is a schematic cross-sectional view of a liquid crystal displaydevice showing a second embodiment of the present invention;

FIG. 11 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, and directions of retardation axes offirst and second retardation plates in the liquid crystal display deviceaccording to the second embodiment;

FIGS. 12A to 12D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) of display T₂₀ in theliquid crystal display in the liquid crystal display device according tothe second embodiment;

FIG. 13 is a schematic cross-sectional view of a liquid crystal displaydevice showing a third embodiment according to the present invention;

FIG. 14 is a perspective view for explaining characteristics of anoptical film in the liquid crystal display device according to the thirdembodiment;

FIG. 15 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, directions of retardation axes offirst and second retardation plates, directions of optical axes of firstand second optical films;

FIGS. 16A to 16D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the third embodiment;

FIG. 17 is a schematic cross-sectional view of a liquid crystal displaydevice showing a fourth embodiment of the present invention;

FIG. 18 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, directions of retardation axes offirst and second retardation plates, and directions of optical axes ofoptical films in the liquid crystal display device according to thefourth embodiment;

FIGS. 19A to 19D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the fourth embodiment;

FIG. 20 is a schematic cross-sectional view of a liquid crystal displaydevice according to a fifth embodiment of the present invention;

FIG. 21 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, and directions of retardation axes offirst and second retardation plates in the liquid crystal display deviceaccording to the fifth embodiment;

FIGS. 22A to 22D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the fifth embodiment;

FIG. 23 is a schematic cross-sectional view of a liquid crystal displaydevice showing a sixth embodiment according to the present invention;

FIG. 24 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, and directions of retardation axes offirst and second retardation plates in the liquid crystal display deviceaccording to the sixth embodiment;

FIGS. 25A to 25D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the sixth embodiment;

FIG. 26 is a schematic cross-sectional view of a liquid crystal displaydevice showing a seventh embodiment according to the present invention;

FIG. 27 is a view showing aligning treatment directions of first andsecond alignment films, directions of absorption axes of first andsecond polarizing layers, directions of optical axes of first and secondviewing angle compensating layers, and directions of retardation axes offirst and second retardation plates in the liquid crystal display deviceaccording to the seventh embodiment; and

FIGS. 28A to 28D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ in theliquid crystal display device according to the seventh embodiment.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

FIGS. 1 to 8 show a first embodiment according to the present invention,and FIG. 1 is a schematic cross-sectional view of a liquid crystaldisplay device.

This liquid crystal display device is a TN type liquid crystal displaydevice including a liquid crystal cell 1 including a nematic liquidcrystal layer 10 in which liquid crystal molecules are twist-aligned ata twisted angle of substantially 90° sandwiched between a pair oftransparent substrates 2 and 3, a pair of first and second polarizingplates 11 and 15 arranged to sandwich this liquid crystal cell 1, andfirst and second viewing angle compensating plates 19 and 22respectively arranged between the liquid crystal cell 1 and the pair ofpolarizing plates 11 and 15.

FIG. 2 is an enlarged cross-sectional view of a part of the liquidcrystal cell 1. This liquid crystal cell 1 includes a first substrate 2,a second substrate 3 arranged to face this first substrate, and a liquidcrystal layer 10 arranged between the first and second substrates. Thefirst substrate 2 has at least one first transparent electrode 4 and afirst alignment film 7 that covers the first electrode 4 and issubjected to aligning treatment in a predetermined first direction, thefirst transparent electrode 4 and the first alignment film 7 beingprovided on one surface thereof. The second substrate 3 is arranged toface an electrode formation surface of the first substrate 2, and has atleast one second transparent electrode 5 facing the first electrode 4,and a second alignment film 8 that covers the second transparentelectrode 5 and is subjected to an aligning treatment in a seconddirection crossing the first direction for covering the second electrode5 at an angle of substantially 90°, the second transparent electrode 5and the second alignment film 8 being provided on a surface facing thefirst substrate 2. The liquid crystal layer 10 is sandwiched between thefirst alignment film 7 and the second alignment film 8, and liquidcrystal molecules 10 a are twist-aligned at a twisted angle ofsubstantially 90° between the first alignment film 7 and the secondalignment film 8. This liquid crystal layer 10 optically rotates apolarized light that has entered in an initial alignment state of liquidcrystal molecules 10 a at 90°. Moreover, this liquid crystal layer 10apparently changes a value of a retardation produced with respect totransmitted light within the range of substantially λ/2 in accordancewith an alignment state of the liquid crystal molecules 10 a.

This liquid crystal cell 1 is an active matrix liquid crystal cell, andthe electrode 4 provided on the substrate (which will be referred to asa rear substrate hereinafter) 2, located on an opposite side of adisplay observation side, is formed of a plurality of pixel electrodesaligned and formed in a matrix shape along a row direction (a lateraldirection of a screen) and a column direction (the lateral direction ofthe screen). The electrode 5 provided on the other substrate (which willbe referred to as a front substrate hereinafter) 3, located on theobservation side, is a single-film-like opposed electrode formed to facean entire arrangement region of the plurality of pixel electrodes 4.

Although omitted in FIG. 2, a plurality of TFTs (thin film transistors)respectively arranged in accordance with the plurality of pixelelectrodes 4, a plurality of scanning lines through which gate signalsare supplied to the plurality of TFTs in respective rows, and aplurality of signal lines through which data signals are supplied to theplurality of TFTs in respective columns are provided on a surface of therear substrate 2 facing the front substrate 3.

The TFT includes a gate electrode formed on the rear substrate 2, a gateinsulating film formed to cover the gate electrode, an i-typesemiconductor film formed on the gate insulating film to face the gateelectrode, and a drain electrode and a source electrode formed on bothside portions of the i-type semiconductor film through an n-typesemiconductor film. The gate electrode is connected with the scanningline, the drain electrode is connected with the signal line, and thesource electrode is connected with the corresponding pixel electrode 4.

Additionally, color filters 6R, 6G, and 6B of three colors, i.e., red,green, and blue are provided on a surface of the front substrate 3facing the rear substrate 2 in accordance with a plurality of pixelsformed of regions where the plurality of pixel electrodes 4 face theopposed electrode 5, and the opposed electrode 5 is provided to coverthe color filters 6R, 6G, and 6B.

Further, the pair of substrates 2 and 3 are arranged to face each otherwith a predetermined gap provided therebetween, and bonded to each otherthrough a sealing member 9 (see FIG. 1) formed into a frame shapesurrounding an arrangement region of the plurality of pixel electrodes4. The liquid crystal layer 10 is encapsulated in a region between thepair of substrates 2 and 3 surrounded by the sealing member 9.

Furthermore, as to the color filters 6R, 6G, and 6B of three colors,i.e., red, green, and blue, the green filter 6G is formed to be thickerthan the red filter 6R and the blue filter 6B is formed with a largerfilm thickness than that of the green filter 6G, so that a liquidcrystal layer thickness d_(R) of one of the pixels to which the redfilter 6R is provided, a liquid crystal layer thickness d_(G) of one ofthe pixels to which the green filter 6G is provided, and a liquidcrystal layer thickness d_(B) of one of the pixels to which the bluefilter 6B is provided have a relationship of d_(R)≧d_(G)≧d_(B).

A ratio of the liquid crystal layer thickness d_(R) of the pixel towhich the red filter 6R is provided, the liquid crystal layer thicknessd_(G) Of the pixel to which the green filter 6G is provided, and theliquid crystal layer thickness d_(B) of the pixel to which the bluefilter 6B is provided is set to d_(R):d_(G):d_(B)=1.1:1.0:0.9.

Moreover, of the pair of polarizing plates arranged to sandwich theliquid crystal cell 1 therebetween, the first polarizing plate 11arranged to face an outer surface of the liquid crystal cell 1 oppositeto the electrode formation surface of the rear substrate 2 is arrangedso that its absorption axes sets to parallel with a direction crossingan aligning treatment direction of the first alignment film 7 formed onthe rear substrate 2 at an angle of substantially 45°. The secondpolarizing plate 15 arranged to face an outer surface of the liquidcrystal cell 1 opposite to the electrode formation surface of thesubstrate 3 is arranged so that its absorption axes sets to parallelwith a direction crossing the aligning treatment direction of the secondalignment film 8 formed on the front substrate 3 at an angle ofsubstantially 45°. That is, the absorption axes of the first polarizingplate 11 and the second polarizing plate 15 are perpendicular to eachother.

The first polarizing plate 11 includes a first polarizing layer 12having an absorption axes in a direction crossing the aligning treatmentdirection of the first alignment film 7 at an angle of substantially45°, and a pair of base films 13 and 14 that are respectively formed onboth surfaces of the first polarizing layer 12 to sandwich the firstpolarizing layer 12 therebetween, have a phase difference in a planeparallel to substrate surfaces of the pair of substrates 2 and 3 beingsubstantially zero, have a phase difference in a plane perpendicular tothe substrate surfaces of the pair of substrates 2 and 3 (which will bereferred to as a phase difference in a thickness directionthereinafter), and are formed of a transparent resin film, e.g., a TAC(triacetylcellulose) film. The second polarizing plate 15 includes asecond polarizing layer 16 having an absorption axis in a directioncrossing the aligning treatment direction of the second alignment film 8formed on the front substrate 8 at an angle of substantially 45°, and apair of base films 17 and 18 that are provided on both surfaces of thesecond polarizing layer 16 to sandwich this second polarizing layer 16therebetween, have a phase difference in a plane parallel to thesubstrate surfaces being substantially zero, have a phase difference ina plane perpendicular to the substrates (a phase difference in thethickness direction), and are formed of a transparent resin film, e.g.,a TAC film.

The first and second viewing angle compensating plates 19 and 22, whichare respectively arranged between the liquid crystal cell 1 and the pairof polarizing plates 11 and 15, respectively include viewing anglecompensating layers 20 and 23 formed of a discotic liquid crystal layerin which discotic liquid crystal molecules are hybrid-aligned, and apair of base films 21 and 24 that are formed of a transparent resinfilm, e.g., the TAC film, the base films 21 being provided on at leastone surface of the viewing angle compensating layers 20 and the basefilms 24 being provided on at least one surface of the viewing anglecompensating layers 23. Each of the viewing angle compensating layers 20and 23 has a phase difference in a plane parallel with the substratesurfaces and a phase difference in a plane perpendicular to thesubstrate surfaces (a phase difference in the thickness direction).Further more, each of the pair of base films 21 and 24 has a phasedifference in a plane parallel with the substrate surfaces beingsubstantially zero and a phase difference in a plane perpendicular tothe substrate surfaces (a phase difference in the thickness direction).

The first and second viewing angle compensating plates 19 and 22 used inthis embodiment are obtained by providing the base film 21 and 24 on onesurface of the viewing angle compensating layer 20 and 23, respectively.

FIG. 3 is an enlarged cross-sectional view of a part of the first andsecond viewing angle compensating plates 19 and 22, and the base films21 and 24 are respectively provided with alignment films 21 a and 24 athat are subjected to an aligning treatment in one direction, thealignment film 21 a being formed on one surface of the base film 21 andthe alignment film 24 a being formed on one surface of the base film 24,and the discotic liquid crystal layers are respectively provided on thealignment films 21 a and 24 a. In this discotic liquid crystal layer,the discotic liquid crystal molecules 25 are hybrid-aligned so that amolecular axis perpendicular to discotic surfaces of the discotic liquidcrystal molecules 25 is placed on a plane perpendicular to a filmsurface of the base film 21 and parallel to the aligning treatmentdirection of the alignment film 21 a and a tilt angle with respect tothe base film 21 is sequentially increased from the base film 21 sidetoward its opposite side.

Each of the viewing angle compensating layer 20 and 23 of the first andsecond viewing angle compensating plate 19 and 22 has a negative opticalanisotropy having an optical axis providing a minimum refractive indexin an average tilt direction of the molecular axis in the plane wherethe molecular axes of the hybrid-aligned discotic liquid crystalmolecules 25 are present. Here, a line on which the plane where themolecular axes of the discotic liquid crystal molecules 25 are presentcrosses the surface of the viewing angle compensating layer 20 and 23 isreferred to as an optical axis direction.

Furthermore, the first viewing angle compensating plate 19 is arrangedso that a surface of the first viewing angle compensating layer 20 ofthis viewing angle compensating plate 19 where a tilt angle of thediscotic liquid crystal molecules 25 is large (a surface opposite to thebase film 21 side) faces the outer surface of the rear substrate 2 ofthe liquid crystal cell 1. Moreover, the optical axis direction of thefirst viewing angle compensating layer 20 sets to parallel with adirection substantially parallel to or substantially perpendicular tothe aligning treatment direction of the first alignment film 7 formed onthe rear substrate 2. The second viewing angle compensating plate 22 isarranged so that a surface of the second viewing angle compensatinglayer 23 of this viewing angle compensating plate 22 where a tilt angleof the discotic liquid crystal molecules is large (a surface opposite tothe base film 24 side) faces the outer surface of the front substrate 3of the liquid crystal cell 1. Additionally, the optical axis directionof the second viewing angle compensating layer 23 sets to parallel witha direction substantially parallel to or substantially perpendicular tothe aligning treatment direction of the second alignment film 8 formedon the front substrate 3.

FIG. 4 shows aligning treatment directions 7 a and 8 a of the first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the polarizing layers 12 and 16 ofthe first and second polarizing plates 11 and 15, and directions ofoptical axis directions 20 a and 23 a of the viewing angle compensatinglayers 20 and 23 of the first and second viewing angle compensatingplates 19 and 22.

As shown in FIG. 4, the first alignment film 7 formed on the rearsubstrate 2 of the liquid crystal cell 1 is aligned in a first directioncrossing a lateral axis direction (a direction indicated by an alternatelong and short dash line in the drawing) of a screen of the liquidcrystal display device clockwise as seen from the observation side at anangle of substantially 45°. The second alignment film 8 formed on thefront substrate 3 is aligned in a second direction (a direction crossingthe lateral axis direction of the screen counterclockwise as seen fromthe observation side at an angle of substantially 45°) crossing thefirst direction at an angle of substantially 90°. The liquid crystalmolecules 10 a in the liquid crystal layer 10 held between the firstalignment film 7 of the rear substrate 2 and the second alignment film 8of the front substrate 3 are twist-aligned in a layer thicknessdirection of the liquid crystal layer 10 between the first alignmentfilm 7 and the second alignment film 8 at a twisted angle ofsubstantially 90° as indicated by an arrow of a dashed line that shows atwisted direction of a molecular orientation.

In the liquid crystal layer 10 of this liquid crystal cell 1, a value ofa retardation apparently varies in the range of substantially λ/2 withrespect to transmitted light in accordance with an alignment state ofthe liquid crystal molecules 10 a that changes in accordance with avoltage applied to the liquid crystal layer 10 between the electrodes 4and 5 on the pair of substrates 2 and 3.

The first polarizing plate 11 facing the outer surface of the rearsubstrate 2 of the liquid crystal cell 1 is arranged so that theabsorption axis 12 a of the first polarizing layer 12 of this polarizingplate 11 sets to parallel with the lateral axis direction of the screeni.e., crossing the aligning treatment direction 7 a of the firstalignment film 7 of the rear substrate 2 counterclockwise as seen fromthe observation side at an angle of substantially 45°. The secondpolarizing plate 15 facing the outer surface of the front substrate 3 ofthe liquid crystal cell 1 is arranged so that the absorption axis 16 aof the second polarizing layer 16 of this polarizing plate 15 sets toparallel with a direction (a direction substantially perpendicular tothe lateral axis direction of the screen) substantially perpendicular tothe absorption axis 12 a of the polarizing layer 12 of the firstpolarizing plate 11.

Further, the first viewing angle compensating plate 19 between the rearsurface 2 of the liquid crystal cell 1 and the first polarizing plate 11is arranged so that the optical axis direction 20 a of the first viewingangle compensating layer 20 of this viewing angle compensating plate 19sets to parallel with a direction substantially parallel with thealigning treatment direction 7 a of the first alignment film 7 of therear substrate 2. The second viewing angle compensating plate 22 betweenthe front substrate 3 of the liquid crystal cell 1 and the secondpolarizing plate 15 is arranged so that the optical axis direction 23 aof the second viewing angle compensating layer 23 of this viewing anglecompensating plate 22 sets to parallel with a direction substantiallyparallel with the aligning treatment direction 8 a of the secondalignment film 8 of the front substrate 3, i.e., a directionsubstantially perpendicular to the optical axis direction 20 a of theviewing angle compensating layer 20 of the first viewing anglecompensating plate 19.

This liquid crystal display device controls transmission of whiteillumination light emitted from a non-illustrated surface light sourcearranged on a rear side thereof (the opposite side of the observationside) by application of a voltage to the liquid crystal layer 10 betweenthe electrodes 4 and 5 in accordance with each of the plurality of pixelportions, and irradiates light of three colors, i.e., red, green, andblue, colored by the color filters 6R, 6G, and 6B of three colors, i.e.,red, green, and blue, corresponding to the plurality of pixel portionsto the observation side, thereby displaying a color image.

This liquid crystal display device displays a color image having a goodcolor balance because a ratio of the liquid crystal layer thicknessd_(R) of the pixel portion to which the red color filter 6R of theliquid crystal cell 1 is provided (which will be referred to as a redpixel portion hereinafter), the liquid crystal layer thickness d_(G) ofthe pixel portion to which the green filter 6G is provided (which willbe referred to as a green pixel portion hereinafter), and the liquidcrystal layer thickness d_(B) Of the pixel portion to which the bluefilter 6B is provided (which will be referred to as a blue pixelportion) is set to d_(R):d_(G):d_(B)=1.1:1.0:0.9.

That is, FIG. 5 shows a relationship between the ratio of the liquidcrystal layer thickness d_(R), d_(G), and d_(B) of the pixel portionshaving the respective colors, i.e., red, green, and blue, and a displaychromaticity when light is emitted from each of the pixel portionshaving the colors, i.e., red, green, and blue, to display a white color.

As shown in FIG. 5, comparing examples where the ratio of the liquidcrystal layer thicknesses d_(R), d_(G), and d_(B) of the pixel portionshaving red, green, and blue colors is set tod_(R):d_(G):d_(B)=0.9:1.0:1.1, d_(R):d_(G):d_(B)=1.0:1.0:1.0, andd_(R):d_(G):d_(B)=1.1:1.0:0.9 with each other, a white displaychromaticity when the ratio of the liquid crystal layer thicknessesd_(R), d_(G), and d_(B) of the pixel portions having the respectivecolors is set to d_(R):d_(G):d_(B)=1.1:1.0:0.9 is a chromaticity closeto that of light from a light source (white illumination light from thesurface light source) as compared with a white display chromaticity whenthe ratio of the liquid crystal layer thicknesses d_(R), d_(G), andd_(B) is set to any other value, and hence a color image having a goodcolor balance is displayed.

It is to be noted that this liquid crystal display device is of anormally white type where the first polarizing plate 11 and the secondpolarizing plate 15 are arranged so that the absorption axes 12 a and 16a of the respective polarizing layers 12 and 16 become substantiallyperpendicular to each other. This liquid crystal display device displayswhite when no voltage is applied to the liquid crystal layer 10 betweenthe electrodes 4 and 5 of each pixel portion, and displays black when avoltage that is sufficiently high for the substantially all liquidcrystal molecules 10 a in the layer thickness direction of the liquidcrystal layer 10 to rise to be aligned substantially perpendicularlywith respect to the substrate surfaces (which will be referred to as asaturation voltage) is applied to the liquid crystal layer 10 betweenthe electrodes 4 and 5 of each pixel portion.

In the liquid crystal cell 1 having the liquid crystal layer 10 in whichthe liquid crystal molecules 10 a are twist-aligned with a twisted angleof substantially 90° between the pair of substrates 2 and 3, a behaviorof the liquid crystal molecules 10 a in the liquid crystal layer 10 nearthe pair of substrates 2 and 3 is suppressed by an anchoring effect ofthe alignment films 7 and 8. Thus, even when the saturation voltage isapplied to the liquid crystal layer 10 between the electrodes 4 and 5,the liquid crystal molecules 10 a near the pair of substrates 2 and 3 donot rise to be aligned, and an in-plane retardation (which will bereferred to as a residual retardation) due to the liquid crystalmolecules 10 a in the liquid crystal layer 10 near the substrates 2 and3 is present.

Furthermore, when the saturation voltage is applied to the liquidcrystal layer 10 between the electrodes 4 and 5, the liquid crystallayer 10 has a negative phase difference (which will be referred to as aphase difference in the liquid crystal layer thickness direction) in aplane perpendicular to the substrate surfaces.

In the liquid crystal display device in which the first and secondpolarizing plates 11 and 15 are arranged so that the absorption axes 12a and 16 a of the polarizing layers 12 and 16 sets to parallel with adirection forming an angle of substantially 45° with respect to thealigning treatment directions 7 a and 8 a of the alignment films 7 and 8in particular, the phase difference in the liquid crystal layerthickness direction greatly functions with respect to light thatobliquely enters the substrate surfaces, thereby reducing viewing anglecharacteristics.

Thus, in the liquid crystal display device according to this embodiment,the first and second viewing angle compensating plates 19 and 22 arerespectively arranged between the first and second polarizing plates 11and 15 arranged on the front and the rear sides of the liquid crystalcell 1 and the rear substrate 2 and the front substrate 3 of the liquidcrystal cell 1 so that the first and second viewing angle compensatingplates 19 and 22 cancel out the residual retardation. Moreover, thephase difference of the liquid crystal layer 10 in the planeperpendicular to the substrate surfaces when the saturation voltage (avoltage sufficiently high for the liquid crystal molecules 10 a to riseto be aligned) is applied to the liquid crystal layer 10 between theelectrodes 4 and 5 of the liquid crystal cell 1 is canceled out by thephase differences of the plurality of optical layers within the planeperpendicular to the substrate surfaces. The plurality of optical layersinclude the base films 14 and 18 on the surfaces of the first and secondpolarizing plates 11 and 15 facing the liquid crystal cell 1 between thefirst polarizing layer 12 of the first polarizing plate 11 and thesecond polarizing layer 16 of the second polarizing plate 15, therespective viewing angle compensating layers 20 and 23 of the first andsecond viewing angle compensating plates 19 and 22, and the base films21 and 24 of the first and second viewing angle compensating plates 19and 22.

That is, a value of a product of the phase difference of the liquidcrystal layer 10 in the liquid crystal layer thickness direction and theliquid crystal layer thickness (an average value of the liquid crystallayer thicknesses d_(R), d_(G), and d_(B) of the pixel portions havingthe respective colors to which the red, the green, and the blue colorfilters 6R, 6G, and 6B are provided) d is determined as a retardation inthe liquid crystal layer thickness direction, and a value of a productof the phase difference in the thickness direction of each of theplurality of optical layers and each layer thickness is determined as aretardation in the thickness direction. At this time, when a valueobtained by adding the retardation in the liquid crystal layer thicknessdirection and the retardations in the thickness direction of theplurality of the optical layers is set to fall within the range of −80nm to +80 nm (0±80 nm), or preferably to 0 nm, the retardation in thethickness direction of the liquid crystal layer 10 at the time ofapplication of the saturation voltage is canceled out.

FIG. 6 shows a relationship between a product Δnd of an anisotropicrefractive index Δn and the liquid crystal layer thickness d of a liquidcrystal material constituting the liquid crystal layer 10 and a liquidcrystal layer thickness direction retardation Rth_(LC) of the liquidcrystal layer 10 when the saturation voltage is applied on theassumption that a pre-tilt angle of the liquid crystal molecules 10 a is5.5° and the saturation voltage is 4V. The liquid crystal Layerthickness direction retardation Rth_(LC) of the liquid crystal layer 10when the saturation voltage is applied varies as shown in the drawing inaccordance with a value of the product Δnd of the liquid crystal layer10. That is, the retardation Rth_(LC) in the liquid crystal layerthickness direction linearly varies with respect to a change in a valueof the product Δn of the liquid crystal layer 10. Thus, the retardationRth_(LC) is obtained by multiplying the value of the product Δnd of theliquid crystal layer 10 by a coefficient corresponding to an inclinationof the straight line depicted in FIG. 6.

Thus, it is good enough to set an absolute value obtained by addingvalues of the retardations in the thickness direction of the pluralityof optical layers excluding the liquid crystal layer 10 between thefirst polarizing layer 12 of the first polarizing plate 11 and thesecond polarizing layer 16 of the second polarizing plate 15 to matchwith an absolute value obtained by multiplying a value of Δnd of theliquid crystal layer 10 by a coefficient preset in accordance with thepre-tilt angle of the liquid crystal molecules 10 a and the saturationvoltage, or set a difference between the respective absolute values tofall within the range of −80 nm to +80 nm.

The next Table 1 shows a relationship between the retardation Rth_(LC)in the liquid crystal layer thickness direction of the liquid crystallayer 10 having the liquid crystal molecules 10 a with a pre-tilt angleand a saturation voltage being changed and a coefficient value that ismultiplied with respect to a value Δnd of the liquid crystal layer tocalculate a value of the retardation in the thickness direction of eachof the plurality of optical layers.

TABLE 1 Saturation Pre-tilt voltage Rth_(LC) Coefficient 0.5° 3 V−299.43 0.72 5.5° 3 V −311.03 0.75 10.5° 3 V −321.85 0.77 0.5° 4 V−338.46 0.81 5.5° 4 V −345.40 0.83 10.5° 4 V −352.11 0.85 0.5° 5 V−358.35 0.86 5.5° 5 V −363.41 0.87 10.5 5 V −368.32 0.86

As shown in Table 1, when the pre-tilt angle of the liquid crystalmolecules 10 a falls within the range of 0.5° to 10.5° and thesaturation voltage falls within the range of 3V to 5V, a value of theretardation in the liquid crystal layer thickness direction of theliquid crystal layer 10 at the time of applying the saturation voltageis calculated by multiplying a coefficient falling within the range of0.72 to 0.86 by a value of Δnd of the liquid crystal layer. Here, thevalue of the retardation in the liquid crystal thickness direction ofthe liquid crystal layer 10 at the time of applying the saturationvoltage and a total value of the retardations in the thickness directionof the plurality of optical layers excluding the liquid crystal layer 10have substantially the same absolute values, and have opposite signs.

Thus, in this embodiment, the total value of the retardations in thethickness direction of the plurality of optical layers between the firstpolarizing layer 12 and the second polarizing layer 16 excluding theliquid crystal layer 10 is set to a value obtained by multiplying thevalue of Δnd of the liquid crystal layer 10 by a coefficient fallingwithin the range of 0.72 to 0.86, and a total value of the values of theretardations in the thickness direction of the plurality of opticallayers excluding the liquid crystal layer 10 and the retardation in theliquid crystal layer thickness direction of the liquid crystal layer 10at the time of applying the saturation voltage is set to fall within therange of 0±80 nm (−80 nm to +80 nm). In this case, as the value of theretardation in the liquid crystal layer thickness direction of theliquid crystal layer 10 at the time of applying the saturation voltage,a value obtained by multiplying a coefficient 0.83 by the value of Δndof the liquid crystal layer 10.

Additionally, FIG. 7 shows a transmittance of the liquid crystal displaydevice with respect to a value Ro+Δnd that is obtained by adding anin-plane retardation Ro acquired by adding values of in-planeretardations of the plurality of optical layers excluding the liquidcrystal layer 10 between the first polarizing layer 12 of the firstpolarizing plate 11 and the second polarizing layer of the secondpolarizing plate in the liquid crystal display device to the product Δndof the liquid crystal layer 10. The plurality of optical layers includethe base films 14 and 18 on the surfaces of the first and secondpolarizing plates 11 and 15 facing the liquid crystal cell 1, theviewing angle compensating layers 20 and 23 of the first and secondviewing angle compensating plates 19 and 22, and the base films 21 and24 of the first and second viewing angle compensating plates 19 and 22.The liquid crystal display device demonstrates a high transmittance whena value of Ro+Δnd falls within the range of 350 nm to 600 nm, and a peakwhen a value of Ro+Δnd is 480 nm in particular.

Thus, in this embodiment, a value obtained by adding a total value ofthe in-plane retardations each of which is a product of an in-planephase difference in a plane parallel to the substrate surfaces of eachof the plurality of optical layers between the first polarizing layer 12and the second polarizing layer 16 and a layer thickness of the opticallayer to Δnd of the liquid crystal layer 10 is set to the range of 350nm to 600 nm, or preferably 480 nm.

In more detail, in the liquid crystal display device according to thisembodiment, an optical function of the base films 13 and 17 placedoutside the first and second polarizing layers 12 and 16 of the firstand second polarizing plates 11 and 15 does not concern visibility of anobserver. Further, the plurality of optical layers between the firstpolarizing layer 12 and the second polarizing layer 16 concernvisibility of the observer, the plurality of optical layers includingthe base films 14 and 18 of the first and second polarizing plates 11and 15, the first and second viewing angle compensating layers 20 and 23of the first and second viewing angle compensating plates 19 and 22, thebase films 21 and 24 of these compensating layers 20 and 23, and theliquid crystal layer 10.

As depicted in FIG. 14 showing X, Y, and Z coordinates of an opticalmedium 100 and refractive indices in respective coordinate axisdirections, in regard to each of the plurality of optical layers of theoptical medium 100, assuming that one and the other of two directionsperpendicular to each other on a plane parallel to the substratesurfaces are an X axis and a Y axis, a thickness direction perpendicularto the substrate surfaces is a Z axis, a refractive index in the X axisdirection is nx, a refractive index in the Y axis direction is ny, arefractive index in the Z axis direction is nz, and a layer thickness ofthe optical layer is d, a retardation Rthi in the thickness direction ofeach optical layer is expressed as {(nx+ny)/2−nz}·d. Assuming that Rthis a total retardation in the thickness direction obtained by addingvalues of the retardations Rthi in the thickness direction of theseoptical layers and Δnd is a product of an anisotropic refractive indexΔn of a liquid crystal material constituting the liquid crystal layer 10and an average liquid crystal layer thickness d, the total retardationRth in the thickness direction is set to fall within the rangesatisfying the following expression:Rth=0.83Δnd±80 nm.That is, the total retardation Rth in the thickness direction is set tofall within the range of 0.83 Δnd−80 nm to 0.83 Δnd+80 nm.

Furthermore, in retard to the plurality of optical layers between thefirst polarizing layer 12 and the second polarizing layer 16, assumingthat Roi is an in-plane retardation of each optical layer expressed as(nx−ny)·d and Ro is an in-plane retardation obtained by adding values ofin-plane retardations Roi of the respective optical layers, thetotalized in-plane retardation Ro is set to the range satisfying thefollowing expression:Ro+Δnd=350 nm to 600 nm.

In the liquid crystal display device according to this embodiment, avalue of Δnd of the liquid crystal layer 10 of the liquid crystal cell 1is 380 mm; values of the retardation Rthi in the thickness direction andthe in-plane retardation Roi of the first and the second viewing anglecompensating layers 20 and 23, Rthi=70 nm and Roi=−47 nm; values of theretardation Rthi in the thickness direction and the in-plane retardationRoi of the base films 14 and 18 on the surfaces of the first and secondpolarizing layers 12 and 16 facing the liquid crystal cell 1 and thebase films 21 and 24 of the first and second viewing angle compensatinglayers 20 and 23, Rthi=89 mm and Roi=9 nm.

Thus, the retardation Rth in the thickness direction obtained by addingvalues of the retardations Rthi in the thickness direction, which isexpressed as {(nx+ny)/2−nz}·d, of the plurality of the optical layersbetween the first polarizing layer 12 and the second polarizing layer 16excluding the liquid crystal layer 10 is 353 nm, and the in-planeretardation Ro obtained by adding values of the in-plane retardationsRoi of the plurality of optical layers is 12 nm. Accordingly, the value0.83 Δnd obtained by multiplying the value of Δnd of the liquid crystallayer 10 by the preferable coefficient 0.83 is 315 nm, and the value 353nm as the added retardation Rth in the thickness direction falls withinthe range of a value obtained by adding 80 nm to −315 nm or +315 nm as avalue of 0.83 Δnd. Furthermore, the value obtained by totalizing theadded in-plane retardation Ro and Δnd is 392 nm, and falls within therange of 350 nm to 600 nm that defines the range of Ro+Δnd.

Since this liquid crystal display device has the above-explainedstructure, angle dependency of the transmittance is improved, and adisplay wide viewing angle is increased.

FIGS. 8A to 8D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation (a gradationwith 50% brightness of white display) display T₅₀, and 20% gradation (agradation with 20% brightness of white display) display T₂₀ of theLiquid crystal display device. FIG. 8A shows viewing anglecharacteristics in a right-and-left direction of the screen, FIG. 8Bshows viewing angle characteristics in an up-and-down direction of thescreen, FIG. 8C shows viewing angle characteristics in a direction froma lower left side to a lower right side of the screen, and FIG. 8D showsviewing angle characteristics in a direction from a lower right side toan upper left side of the screen.

It is to be noted that a negative angle is an angle in the leftdirection and a positive angle is an angle in the right direction inFIG. 8A. In FIG. 8B, a negative angle is an angle in the lower directiona positive angle is an angle in the upper direction. In FIG. 8C, anegative angle is an angle in the lower left direction and a positiveangle is an angle in the upper right direction. In FIG. 8D, a negativeangle is an angle in the lower right direction and a positive angle isan angle in the upper left direction.

As shown in FIGS. 8A to 8D, the liquid crystal display device has theviewing angle characteristics that the angle dependency of atransmittance in each direction, i.e., the right-and-left direction, theup-and-down direction, the direction from the lower left to the lowerright, and the direction from the lower right to the upper left in thescreen is improved, i.e., inversion of the intermediate gradation doesnot occur in a wide angle range in each of these directions. Inparticular, the viewing angle is wide in the right-and-left direction,the direction from the lower left to the lower right, and the directionfrom the lower right to the upper left.

Modification of First Embodiment

It is to be noted that a value of Δnd of the liquid crystal layer 10 inthe liquid crystal cell 1 is set to 380 nm in the liquid crystal displaydevice, but the value of Δnd of the liquid crystal layer 10 may be setto any other value.

FIGS. 9A to 9D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ in a liquid crystal display device in which avalue of Δnd of the liquid crystal layer 10 is set to 505 nm and theother structures are the same as those in the foregoing embodiment. FIG.9A shows viewing angle characteristics in the right-and-left directionof the screen, FIG. 9B shows viewing angle characteristics in theup-and-down direction of the screen, FIG. 9C shows viewing anglecharacteristics in the direction from the lower left to the lower rightof the screen, and FIG. 9D shows viewing angle characteristics in thedirection from the lower right to the upper left of the screen.

As shown in FIGS. 9A to 9D, the liquid crystal display device accordingto this modification has viewing angle characteristics that angledependency of a transmittance in each direction, i.e., theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left in the screen is improved and inversion of theintermediate gradation does not occur in a wide angle range in each ofthese directions. Moreover, contrast is higher than that of the liquidcrystal display device according to the foregoing embodiment.

Second Embodiment

FIGS. 10 to 12 show a second embodiment according to the presentinvention, and they are schematic cross-sectional views of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where a first retardation plate 26 is arranged between thefirst polarizing plate 11 and the first viewing angle compensating plate19 and a second retardation plate 27 is arranged between the secondpolarizing plate 15 and the second viewing angle compensating plate 22in the liquid crystal display device according to the first embodiment.A plurality of optical layers between a first polarizing layer 12 and asecond polarizing layer 16 excluding a liquid crystal layer 10 includebase films 14 and 18 on surfaces of the first and second polarizinglayers 12 and 16 facing a liquid crystal cell 1, the first and secondviewing angle compensating layers 20 and 23, base films 21 and 24 ofthese compensating layers 20 and 23, and the first and secondretardation plates 26 and 27. It is to be noted that other structures ofthe liquid crystal display device according to this embodiment aresubstantially the same as those in the first embodiment

FIG. 11 shows aligning treatment directions 7 a and 8 a of first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the polarizing layers 12 and 16 ofthe first and second polarizing plates 11 and 15, optical axisdirections 20 a and 23 a of the viewing angle compensating layers 20 and23 of the first and second viewing angle compensating plates 19 and 22,and directions of retardation axes 26 a and 27 a of the first and secondretardation plates 26 and 27 in the liquid crystal display deviceaccording to this embodiment.

As shown in FIG. 11, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the polarizinglayers 12 and 16 of the first and second polarizing plates 11 and 15,and the optical axis directions 20 a and 23 a of the viewing anglecompensating layers 20 and 23 of the first and second viewing anglecompensating plates 19 and 22 are the same as those in the firstembodiment. The first retardation plate 26 is arranged so that itsretardation axis 26 a sets to parallel with a direction substantiallyparallel with the optical axis direction 20 a of the first viewing anglecompensating layer 20 of the first viewing angle compensating plate 19.The second retardation plate 27 is arranged so that is retardation axis27 a sets to parallel with a direction substantially parallel with theoptical axis direction 23 a of the second viewing angle compensatinglayer 23 of the second viewing angle compensating plate 22.

Additionally, in this embodiment, a value of Δnd of the liquid crystallayer 10 of the liquid crystal cell 1 is set to 420 nm, and values of aretardation Rthi in a thickness direction and an in-plane retardationRoi of each of the first and second viewing angle compensating layers 20and 23 are set to Rthi=70 nm and Roi=−47 nm. Further, values of aretardation Rthi in the thickness direction and an in-plane retardationRoi of each of base films 14 and 18 of the first and second polarizinglayers 12 and 16 facing the liquid crystal cell 1 and each of base films21 and 24 of the first and second viewing angle compensating layers 20and 23 are set to Rthi=89 nm and Roi=9 nm. Furthermore, values of aretardation Rthi in the thickness direction and an in-plain retardationRoi of each of the first and second retardation plates 26 and 27 are setto Rthi=175 nm and Roi=35 nm. As explained above, a total value of theretardation value in the thickness direction of each of the plurality ofoptical layers between the first polarizing layer 12 and the secondpolarizing layer 16 excluding the liquid crystal layer 10 and theretardation value in the liquid crystal layer direction of the liquidcrystal layer 10 at the time of applying a voltage is set to the rangeof −80 nm to +80 nm.

FIGS. 12A to 12D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of the liquid crystal display device accordingto this embodiment. FIG. 12A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 12B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 12Cshows viewing angle characteristics in a direction from the lower leftto the lower right of the screen, and FIG. 12D shows viewing anglecharacteristics in a direction from the lower right to the upper left ofthe screen.

As shown in FIGS. 12A to 12D, in the liquid crystal display deviceaccording to this embodiment, angle dependency of a transmittance ineach direction, i.e., the right-and-left direction, the up-and-downdirection, the direction from the lower left to the lower right, and thedirection from the lower right to the upper left of the screen isimproved. Furthermore, this liquid crystal display device has viewingangle characteristics that inversion of the intermediate gradation doesnot occur in a wide angle range in each of these directions, and aviewing angle is wide and contrast is high in the right-and-leftdirection, the direction from the lower left to the lower right, and thedirection from the lower right to the upper left.

Third Embodiment

FIGS. 13 to 16 show a third embodiment according to the presentinvention, and FIG. 13 is a schematic cross-sectional view of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where first and second optical films 28 and 29 having a phasedifference are further arranged between the first retardation plate 26and the first viewing angle compensating plate 19 and between the secondretardation plate 27 and the second viewing angle compensating plate 22in the liquid crystal display device according to the second embodiment.A plurality of optical layers between a first polarizing layer 12 and asecond polarizing layer 16 excluding a liquid crystal layer 10 includebase films 14 and 18 on surfaces of the first and second polarizinglayers 12 and 16 facing a pair of substrates 2 and 3 of a liquid crystalcell 1, the first and second viewing angle compensating layers 20 and 23and their base films 21 and 24, the first and second retardation plates26 and 27, and the first and second optical films 28 and 29. It is to benoted that other structures of the liquid crystal display deviceaccording to this embodiment are substantially the same as those of thesecond embodiment.

As shown in FIG. 14, in each of the first and second optical films 28and 29 as an optical medium 100, a relationship between one refractiveindex nx and the other refractive index ny in two directions x and yperpendicular to each other in a plane parallel to a film surface ofeach of the first and second optical films 28 and 29, i.e., parallel tosubstrate surfaces of the liquid crystal cell 1, and a refractive indexnz in a thickness direction z perpendicular to the film surface (thesubstrate surfaces of the liquid crystal cell 1) is nx=ny>nz.

That is, each of the first and second optical films 28 and 29 is aretardation film having an optical axis in the thickness direction zperpendicular to the film surface.

FIG. 15 shows aligning treatment directions 7 a and 8 a of the first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the polarizing layers 12 and 16 ofthe first and second polarizing plates 11 and 15, optical axisdirections 20 a and 23 a of the viewing angle compensating layers 20 and23 of the first and second viewing angle compensating plates 19 and 22,directions of retardation axes 26 a and 27 a of the first and secondretardation plates 26 and 27, and directions of optical axes 28 a and 29a of the first and second optical films 28 and 29.

As shown in FIG. 15, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the polarizinglayers 12 and 16 of the first and second polarizing plates 11 and 15,and the optical axis directions 20 a and 23 a of the viewing anglecompensating layers 20 and 23 of the first and second viewing anglecompensating plates 19 and 22 are the same as those in the first andsecond embodiments.

On the other hand, the first retardation plate 26 is arranged so thatits retardation axis 26 a sets to parallel with a direction crossing alateral axis direction (a direction indicated by an alternate long andshot dash line in the drawing) of the screen counterclockwise as seenfrom an observation side at an angle of substantially 110°. The secondretardation plate 27 is arranged so that its retardation axis 27 a setsto parallel with a direction crossing the lateral axis direction of thescreen clockwise as seen from the observation side at an angle ofsubstantially 20°, i.e., a direction substantially perpendicular to theretardation axis 26 a of the first retardation plate 26. It is to benoted that the directions of the optical axes 28 a and 29 a of the firstand second optical films 28 and 29 are perpendicular to the substratesurfaces of the liquid crystal cell 1.

Furthermore, in this embodiment, a value of Δnd of the liquid crystallayer 10 of the liquid crystal cell 1 is set to 385 nm, and values of aretardation Rthi in a thickness direction and an in-plane retardationRoi of each of the first and second viewing angle compensating layers 20and 23 are set to Rthi=159 nm and Roi=−38 nm. Moreover, values of aretardation Rthi in the thickness direction and an in-plane retardationRoi of each of base films 14 and 18 on surfaces of the first and secondpolarizing layers 12 and 16 facing the liquid crystal cell 1 and each ofbase films 21 and 24 of the first and second viewing angle compensatinglayers 20 and 23 are set to Rthi=89 nm and Roi=9 nm. Additionally,values of a retardation Rthi in the thickness direction and an in-planeretardation Roi of each of the first and second retardation plates 26and 27 are set to Rthi=50 nm and Roi=64 nm. Further, a retardation Rthiin the thickness direction of each of the first and second optical films28 and 29 is set to −160 nm (an in-plane retardation Roi of this opticalfilm 28 or 29 is set to zero). As explained above, a total value of thevalues of the retardations in the thickness direction of the pluralityof optical layers between the first polarizing layer 12 and the secondpolarizing layer 16 excluding the liquid crystal layer 10 and the valueof the retardation in the liquid crystal layer thickness direction ofthe liquid crystal layer 10 is set to the range of 0±80 nm.

FIGS. 16A to 16D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of the liquid crystal display device accordingto this embodiment. FIG. 16A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 16B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 16Cshows viewing angle characteristics in a direction from the lower leftto the lower right of the screen, and FIG. 16D shows viewing anglecharacteristics in a direction from the lower right to the upper left ofthe screen.

As shown in FIGS. 16A to 16D, the liquid crystal display deviceaccording to this embodiment has viewing angle characteristics thatangle dependency of a transmittance in each direction, i.e., theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left in the screen is improved and inversion of theintermediate gradation does not occur in a wide angle range in each ofthe these directions. A viewing angle is wide and contrast is high inthe right-and-left direction, the direction from the lower left to thelower right, and the direction from the lower right to the upper left inparticular.

Fourth Embodiment

FIGS. 17 to 19 show a fourth embodiment according to the presentinvention, and FIG. 17 is a schematic cross-sectional view of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where the optical film 29 provided in the third embodiment isfurther arranged either between the first retardation plate 26 and thefirst viewing angle compensating plate 19 or between the secondretardation plate 27 and the second viewing angle compensating plate 22,e.g., between the first retardation plate 26 and the first viewing anglecompensating plate 19 in the liquid crystal display device according tothe second embodiment. A plurality of optical layers between a firstpolarizing layer 12 and a second polarizing layer 16 excluding a liquidcrystal layer 10 include base films 14 and 18 on surfaces of the firstand second polarizing layers 12 and 16 facing a pair of substrates 2 and3 of a liquid crystal cell 1, the first and second viewing anglecompensating layers 20 and 23 and their base films 21 and 24, the firstand second retardation plates 26 and 27, and the optical film 29. It isto be noted that other structures of the liquid crystal display deviceaccording to this embodiment are substantially the same as thoseaccording to the third embodiment.

FIG. 18 show aligning treatment directions 7 a and 8 a of first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the polarizing layers 12 and 16 ofthe first and second polarizing plates 11 and 15, optical axisdirections 20 a and 23 a of the viewing angle compensating layers 20 and23 of the first and second viewing angle compensating plates 19 and 22,directions of retardation axes 26 a and 27 a of the first and secondretardation plates 26 and 27, and a direction of an optical axis 29 a ofthe optical film 29.

As shown in FIG. 18, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the polarizinglayers 12 and 16 of the first and second polarizing plates 11 and 15,and the optical axis directions 20 a and 23 a of the viewing anglecompensating layers 20 and 23 of the first and second viewing anglecompensating plates 19 and 22 are the same as those in the secondembodiment. Further, the direction of the retardation axis 26 a of thefirst retardation plate 26, the direction of the retardation axis 27 aof the second retardation plate 27 are the same as those in the thirdembodiment. It is to be noted that the direction of the optical axis 29a of the optical film 29 is perpendicular to substrate surfaces of theliquid crystal cell 1.

Furthermore, in this embodiment, a value of Δnd of the liquid crystallayer 10 in the liquid crystal cell 1 is set to 386 nm, and values of aretardation Rthi in a thickness direction and an in-plane retardationRoi of each of the first and second viewing angle compensating layers 20and 23 are set to Rthi=159 nm and Roi=−38 nm. Moreover, values of aretardation Rthi in the thickness direction and an in-plane retardationRoi of each of the base films 14 and 18 on the surfaces of the first andsecond polarizing layers 12 and 16 facing the liquid crystal cell 1 andeach of the base films 21 and 24 of the first and second viewing anglecompensating layers 20 and 23 are set to Rthi=89 nm and Roi=9 nm.Additionally, values of a retardation Rthi in the thickness directionand an in-plane retardation Roi of each of the first and secondretardation plates 26 and 27 are set to Rthi=50 nm and Roi=64 nm.Further, a retardation Rthi in the thickness direction of the opticalfilm 28 is set to −160 nm (an in-plane retardation Roi of this opticalfilm 28 is 0). In this manner, a total value of the value of theretardations in the thickness value of the plurality of optical layersbetween the first polarizing layer 12 and the second polarizing layer 16excluding the liquid crystal layer 10 and a value of a retardation inthe liquid crystal layer thickness direction of the liquid crystal layer10 is set to fall within the range of 0±80 nm.

FIGS. 19A to 19D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of the liquid crystal display device accordingto this embodiment. FIG. 19A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 19B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 19Cshows viewing angle characteristics in a direction from the lower leftto the lower right, and FIG. 19D shows viewing angle characteristics ina direction from the lower right to the upper left.

As shown in FIGS. 19A to 19D, the liquid crystal display deviceaccording to this embodiment has viewing angle characteristics thatangle dependency of a transmittance in each direction, i.e., theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left is improved and inversion of an intermediategradation does not occur in a wide angle range in each of the thesedirection. In particular, a viewing angle is wide and contrast is highin the right-and-left direction, the direction from the lower left tothe lower right, and the direction from the lower right to the upperleft.

Fifth Embodiment

FIGS. 20 to 22 show a fifth embodiment according to the presentinvention, and FIG. 20 is a schematic cross-sectional view of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where first and second viewing angle compensating layers 20and 23 are formed on plate surfaces of first and second retardationplates 26 and 27 in the liquid crystal display device according to thesecond embodiment. A plurality of optical layers between a firstpolarizing layer 12 and a second polarizing layer 6 excluding a liquidcrystal layer 10 include base films 14 and 16 on surfaces of the firstand second polarizing layers 12 and 16 facing a pair of substrates 2 and3 of a liquid crystal cell 1, the first and second viewing anglecompensating layers 20 and 23, and the first and second retardationplates 26 and 27. It is to be noted that other structures of the liquidcrystal display device according to this embodiment are substantiallythe same as those in the second embodiment.

FIG. 21 shows aligning treatment directions 7 a and 8 a of first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the polarizing layers 12 and 16 offirst and second polarizing plates 11 and 15, optical axis directions 20a and 23 a of the first and second viewing angle compensating layers 20and 23, and directions of retardation axes 26 a and 27 a of the firstand second retardation plates 26 and 27 in the liquid crystal displaydevice according to the present invention.

As shown in FIG. 21, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the polarizinglayers 12 and 16 of the first and second polarizing plates 11 and 15,and the optical axis directions 20 a and 23 a of the first and secondviewing angle compensating layers 20 and 23 are the same as those in thefirst embodiment. Furthermore, the direction of the retardation axis 26a of the first retardation plate 26 and the direction of the retardationaxis 27 a of the second retardation plate 27 are the same as those inthe third embodiment.

Moreover, in this embodiment, a value of Δnd of the liquid crystal layer10 in the liquid crystal cell 1 is set to 385 nm, and values of aretardation Rthi in a thickness direction and an in-plane retardationRoi of each of the first and second viewing angle compensating layers 20and 23 are set to Rthi=70 nm and Roi=−47 nm. Additionally, values of aretardation Rthi in the thickness direction and an in-plane retardationRoi of each of the base films 14 and 18 on the surfaces of the first andsecond polarizing layers 12 and 16 facing the liquid crystal cell 1 areset to Rthi=89 nm and Roi=9 nm. Further, values of a retardation Rthi inthe thickness direction and an in-plane retardation Roi of each of thefirst and second retardation plates 26 and 27 are set to Rthi=55 nm andRoi=71 nm. In this manner, a total value of the retardation values inthe thickness direction of the plurality of optical layers between thefirst polarizing layer 12 and the second polarizing layer 16 excludingthe liquid crystal layer 10 and a retardation value in a liquid crystallayer thickness direction of the liquid crystal layer 10 is set to fallwithin the range of 0±80 nm.

In the liquid crystal display device according to this embodiment, sincethe first and second viewing angle compensating layers 20 and 23 areformed on the plate surfaces of the first and second retardation plates26 and 27, the base films 14 and 18 alone on the surfaces of the firstand second polarizing layers 12 and 16 facing the liquid crystal cell 1are determined as the base films having the retardations in thethickness direction among the plurality of optical layers between thefirst polarizing layer 12 and the second polarizing layer 16. Since thenumber of the base films having the retardations in the thicknessdirection is reduced in this manner, the angle dependency of atransmittance is further efficiently improved.

FIGS. 22A to 22D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of the liquid crystal display device accordingto this embodiment. FIG. 22A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 22B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 22Cshows viewing angle characteristics in a direction from the lower leftto the lower right of the screen, and FIG. 22D shows viewing anglecharacteristics of a direction from the lower right to the upper left ofthe screen.

As shown in FIG. 22A to FIG. 22D, the liquid crystal display deviceaccording to this embodiment has viewing angle characteristics thatangle dependency of a transmittance in each direction, i.e., theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left and inversion of an intermediate gradation doesnot occur in a wide angle range in each of these directions. Inparticular, a viewing angle is wide and contrast is high in theright-and-left direction, the direction from the lower left to the lowerright, and the direction from the lower right to the upper left.

Sixth Embodiment

FIGS. 23 to 25 show a sixth embodiment according to the presentinvention, and FIG. 23 is a schematic cross-sectional view of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where base films 13 and 17 are provided on outer surfacesalone of first and second polarizing layers 12 and 16 opposite tosurfaces of the same facing a pair of substrates 2 and 3 of a liquidcrystal cell 1 and first and second retardation plates 26 and 27 arerespectively laminated on the surfaces of the first and secondpolarizing layers 12 and 16 facing the liquid crystal cell 1. Aplurality of optical layers between the first polarizing layer 12 andthe second polarizing layer 16 excluding a liquid crystal layer 10include the first and second retardation plates 26 and 27, the first andsecond viewing angle compensating layers 20 and 23, and base films 21and 24 of these viewing angle compensating layers 20 and 23. It is to benoted that other structures of the liquid crystal display deviceaccording to this embodiment are substantially the same as those in thesecond embodiment.

FIG. 24 shows aligning treatment directions 7 a and 8 a of first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the first and second polarizinglayers 12 and 16, optical axis directions 20 a and 23 a of the first andsecond viewing angle compensating layers 20 and 23, and directions ofretardation axes 26 a and 27 a of the first and second retardationplates 26 and 27 in the liquid crystal display device according to thisembodiment.

As shown in FIG. 24, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the first andsecond polarizing layers 12 and 16, the optical axis directions 20 a and23 a of the first and second viewing angle compensating layers 20 and23, and the directions of the retardation axes 26 a and 27 a of thefirst and second retardation plates 26 and 27 are the same as those inthe first embodiment.

Further, in this embodiment, a value of Δnd of a liquid crystal layer 10of the liquid crystal cell 1 is set to 420 nm, values of a retardationRthi in a thickness direction and an in-plane retardation Roi of each ofthe first and second viewing angle compensating layers 20 and 23 are setto Rthi=159 nm and Roi=−38 nm. Furthermore, values of a retardation Rthiin the thickness direction and an in-plane retardation Roi of each ofthe base films 21 and 24 of the first and second viewing anglecompensating layers 20 and 23 are set to Rthi=89 nm and Roi=9 nm.Moreover, values of a retardation Rthi in the thickness direction and anin-plane retardation Roi of the first and second retardation plates 26and 27 are set to Rthi=175 nm and Roi=35 nm. A total value of theretardation values in the thickness direction of the plurality ofoptical layers between the first polarizing layer 12 and the secondpolarizing layer 16 excluding the liquid crystal layer 10 and aretardation value in a liquid crystal layer thickness direction of theliquid crystal layer 10 is set to fall within the range of 0±80 nm inthis manner.

In the liquid crystal display device according to this embodiment, thebase films 13 and 17 are provided on the cuter surfaces alone of thefirst and second polarizing layers 12 and 16, and the first and secondretardation plates 26 and 27 are laminated on the surfaces of the firstand second polarizing layers 12 and 16 facing the liquid crystal cell 1.Thus, the base films 21 and 24 of the first and second viewing anglecompensating layers 20 and 23 alone are determined as the base filmshaving the retardations in the thickness direction among the pluralityof optical layers between the first polarizing layer 12 and the secondpolarizing layer 16. Since the number of base films having theretardations in the thickness direction is reduced in this manner, theangle dependency of a transmittance is further effectively improved.

FIGS. 25A to 25D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of a liquid crystal display device accordingto this embodiment. FIG. 25A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 25B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 25Cshows viewing angle characteristics of a direction from the lower leftto the lower right of the screen, and FIG. 25D shows viewing anglecharacteristics in a direction from the lower right to the upper left ofthe screen.

As shown in FIGS. 25A to 25D, the liquid crystal display deviceaccording to this embodiment has viewing angle characteristics that theangle dependency of a transmittance in each direction, i.e. theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left of the screen is improved and inversion of anintermediate gradation does not occur in a wide angle range in each ofthese directions. In particular, a viewing angle is wide and contrast ishigh in the right-and-left direction, the direction from the lower leftto the lower right, and the direction from the lower right to the upperleft.

Seventh Embodiment

FIGS. 26 to 28 show a seventh embodiment according to the presentinvention, and FIG. 26 is a schematic cross-sectional view of a liquidcrystal display device.

The liquid crystal display device according to this embodiment has astructure where base films 13 and 17 are provided on outer surfacesalone of first and second polarizing layers 12 and 16 opposite tosurfaces of the same facing a pair of substrates 2 and 3 of a liquidcrystal cell 1, first and second retardation plates 26 and 27 arelaminated on the surfaces of the first and second polarizing layers 12and 16 facing the liquid crystal cell 1, and first and second viewingangle compensating layers 20 and 23 are formed on surfaces of the firstand second retardation plates 26 and 27 facing the liquid crystal cell 1in the liquid crystal display device according to the second embodiment.A plurality of optical layers between the first polarizing layer 12 andthe second polarizing layer 16 excluding a liquid crystal layer 10include the first and second retardation plates 26 and 27 and the firstand second viewing angle compensating layers 20 and 23. It is to benoted that other structures of the liquid crystal display deviceaccording to this embodiment are substantially the same as those in thesecond embodiment.

FIG. 27 shows aligning treatment directions 7 a and 8 a of first andsecond alignment films 7 and 8 of the liquid crystal cell 1, directionsof absorption axes 12 a and 16 a of the first and second polarizinglayers 12 and 16, optical axis directions 20 a and 23 a of the first andsecond viewing angle compensating layers 20 and 23, and directions ofretardation axes 26 a and 27 a of the first and second retardationplates 26 and 27 in the liquid crystal display device according to thisembodiment.

As shown in FIG. 27, the aligning treatment directions 7 a and 8 a ofthe first and second alignment films 7 and 8 of the liquid crystal cell1, the directions of the absorption axes 12 a and 16 a of the first andsecond polarizing layers 12 and 16, and the optical axis directions 20 aand 23 a of the first and second viewing angle compensating layers 20and 23 are the same as those in the first embodiment. The firstretardation plate 26 is arranged so that its retardation axis 26 a setsto parallel with a direction crossing a lateral axis direction of thescreen counterclockwise as seen from an observation side at an angle ofsubstantially 100°. The second retardation plate 27 is arranged so thatits retardation axis 27 a sets to parallel with a direction crossing thelateral axis direction of the screen counterclockwise as seen from theobservation side at an angle of substantially 10°, i.e., a directionsubstantially perpendicular to the retardation axis 26 a of the firstretardation plate 26.

Further, in this embodiment, a value of Δnd of the liquid crystal layer10 of the liquid crystal cell is set to 430 nm, and values of aretardation Rthi in a thickness direction and an in-plane retardationRoi of each of the first and second viewing angle compensating layers 20and 23 are set to Rthi=70 nm and Roi=−47 nm. Furthermore, values of aretardation Rthi in the thickness direction and an in-plane retardationRoi of each of the first and second retardation plates 26 and 27 are setto Rthi=70 nm and Roi=48 nm. In this manner, a total value of theretardation values in the thickness direction of the plurality ofoptical layers between the first polarizing layer 12 and the secondpolarizing layer 16 excluding the liquid crystal layer 10 and aretardation value in a liquid crystal layer thickness direction of theliquid crystal layer 10 is set to fall within the range of 0±80 nm.

In the liquid crystal display device according to this embodiment, thebase films 13 and 17 are provided on the outer surfaces alone of thefirst and second polarizing layers 12 and 16 opposite to the surfacesfacing the pair of substrates 2 and 3 of the liquid crystal cell 1, thefirst and second retardation plates 26 and 27 are laminated on thesurfaces of the first and second polarizing layers 12 and 16 facing theliquid crystal cell 1, and the first and second viewing anglecompensating layers 20 and 23 are formed on the surfaces of the firstand second retardation plates 26 and 27 facing the liquid crystal cell1. Thus, base films having retardations in the thickness direction areeliminated from the plurality of optical layers between the firstpolarizing layer 12 and the second polarizing layer 16, and the basefilms 21 and 24 alone of the first and second viewing angle compensatinglayers 20 and 23 are adopted. As explained above, since the number ofthe base films having the retardations in the thickness direction isreduced, the angle dependency of a transmittance is further effectivelyimproved.

FIGS. 28A to 28D are viewing angle characteristic views at the time ofwhite display T_(W), black display T_(B), 50% gradation display T₅₀, and20% gradation display T₂₀ of the liquid crystal display device accordingto this embodiment. FIG. 28A shows viewing angle characteristics in aright-and-left direction of a screen, FIG. 28B shows viewing anglecharacteristics in an up-and-down direction of the screen, FIG. 28Cshows viewing angle characteristics in a direction from the lower leftto the lower right of the screen, and FIG. 28D shows viewing anglecharacteristics in a direction from the lower right to the upper left ofthe screen.

As shown in FIGS. 28A to 28D, the liquid crystal display deviceaccording to this embodiment has viewing angle characteristics that theangle dependency of a transmittance in each direction, i.e., theright-and-left direction, the up-and-down direction, the direction fromthe lower left to the lower right, and the direction from the lowerright to the upper left of the screen is improved and inversion of theintermediate gradation does not occur in a wide angle range in each ofthese directions. In particular, a viewing angle is wide and contrast ishigh in the right-and-left direction, the direction from the lower leftto the lower right, and the direction from the lower right to the upperleft.

Other Embodiments

Although each of the first and second viewing angle compensating layers20 and 23 according to each of the foregoing embodiments is formed ofdiscotic liquid crystal layer in when discotic liquid crystal molecules25 are hybrid-aligned, the first and second viewing angle compensatinglayers are not restricted to the discotic liquid crystal layer, and itmay be formed of a liquid crystal layer in which, e.g., elongatedspherical liquid crystal molecules are inclined and aligned in onedirection with respect to a plane parallel to the substrate surfaces ofthe liquid crystal cell 1.

Furthermore, although the liquid crystal display device according toeach of the foregoing embodiments is of a normally white type in whichthe first polarizing layer 12 and the second polarizing layer 16 arearranged so that their absorption axes 12 a and 16 a are substantiallyperpendicular to each other, the liquid crystal display device may be ofa normally black type in which the first polarizing layer 12 and thesecond polarizing layer 16 are arranged so that their absorption axes 12a and 16 a are substantially parallel to each other.

As explained above, the liquid crystal display device according to thepresent invention includes: a liquid crystal cell that includes a pairof substrates each having at least one electrode and an alignment filmthat covers this electrode being provided on each of inner surfacesfacing each other, and a liquid crystal layer that is sandwiched betweenthese substrates and includes liquid crystal molecules twist-aligned atsubstantially 90°; first and second polarizing plates that are arrangedon both sides of the liquid crystal cell, and each of which includes apolarizing layer having a transmission axis allowing transmission oflinear polarized light and an absorption axis in a directionperpendicular to the transmission axis and at least one base film thatholds this polarizing layer; and first and second viewing anglecompensating layers that are respectively arranged between the liquidcrystal cell and the first and second polarizing plates, and each ofwhich has a phase difference within a plane parallel to the substratesurfaces of the liquid crystal cell and a phase difference within aplane perpendicular to the substrate surfaces. A total value ofretardations in a thickness direction, each of which is a product of aphase difference within the plane perpendicular to the substratesurfaces and a layer thickness, of a plurality of optical layers betweenthe first and second polarizing layers, including at least the first andsecond viewing angle compensating layers but excluding the liquidcrystal layer, is set to a value that cancels out a retardation in aliquid crystal layer thickness direction, which is a product of a phasedifference within the plane perpendicular to the substrate surfaces anda liquid crystal layer thickness, of the liquid crystal layer when avoltage that is sufficiently high to raise and align the liquid crystalmolecules with respect to the substrate surfaces is applied to theliquid crystal layer between the electrodes of the first and secondsubstrates.

In this liquid crystal display device, it is preferable for theretardation in the thickness direction of each of the plurality ofoptical layers and the retardation in the liquid crystal layer thicknessdirection of the liquid crystal layer to be set so that a value obtainedby adding a total value of the retardations in the thickness directionof the plurality of optical layers and the value of the retardation inthe liquid crystal layer thickness direction of the liquid crystal layerfails within the range of −80 nm to +80 nm.

Furthermore, in this liquid crystal display device, it is preferable forthe value of the retardation in the liquid crystal layer thicknessdirection of the liquid crystal layer when a voltage that issufficiently high to raise and align the liquid crystal molecules isapplied and the total value of the retardations in the thicknessdirection of the plurality of optical layers between the first andsecond polarizing layers excluding the liquid crystal layer to be set sothat a difference between absolute values of these values is not greaterthan 80 nm and these values have a positive and a negative signsopposite to each other. In this case, it is preferable for theretardation in the liquid crystal layer thickness direction to be avalue calculated by multiplying a value of a product Δnd of ananisotropic refractive index Δn of a liquid crystal materialconstituting the liquid crystal layer and a liquid crystal layerthickness d by a coefficient in the range of 0.72 to 0.89 that isselected in accordance with a pre-tilt angle of the liquid crystalmolecules with respect to the substrate surfaces and a value of thevoltage that is sufficiently high to raise and align the liquid crystalmolecules. Moreover, in regard to each of the plurality of opticallayers excluding the liquid crystal layer between the first polarizinglayer and the second polarizing layer, assuming that one and the otherof two directions perpendicular to each other within a plane parallel tothe substrate surfaces are an X axis and a Y axis, a thickness directionperpendicular to the substrate surfaces is a Z axis, a refractive indexin the X axis direction is nx, a refractive index in the Y axisdirection is ny, a refractive index in the Z axis direction is nz, and alayer thickness of the optical layer is d, it is preferable for a totalvalue of retardations in the thickness direction of the respectiveoptical layer each of which is expressed as {(nx+ny)/2−nz}·d to be setto a value that is substantially equal to a value calculated bymultiplying a value of the product Δnd of the anisotropic refractiveindex Δn of the liquid crystal material constituting the liquid crystallayer and the liquid crystal layer thickness d by a coefficient in therange of 0.72 to 0.89 selected in accordance with a pre-tilt angle ofthe liquid crystal molecules with respect to the substrate surfaces anda value of the voltage that is sufficiently high to raise and align theliquid crystal molecules. Additionally, it is preferable for the totalvalue of the retardation values in the thickness direction of therespective optical layers between the first and second polarizing layersexcluding the liquid crystal layer to be set substantially equal to avalue calculated by multiplying the product Δnd of the anisotropicrefractive index Δn of the liquid crystal material constituting theliquid crystal layer and the liquid crystal layer thickness d by acoefficient 0.83.

In the liquid crystal display device according to the present invention,it is preferable for a total value of in-plane retardations of therespective optical layers between the first and second polarizing layersincluding the liquid crystal layer to be set to the range of 350 nm to600 nm, the in-plane retardation of each optical layer being a productof an in-plane phase difference within a plane parallel to the substratesurfaces and a layer thickness of each optical layer.

In the liquid crystal display device according to the present invention,the liquid crystal cell includes: a first substrate having at least onefirst electrode and a first alignment film that covers the firstelectrode and is subjected to an aligning treatment in a predeterminedfirst direction being provided on one surface thereof; a secondsubstrate that is arranged to face an electrode formation surface of thefirst substrate, and has at least one second electrode facing the firstelectrode and a second alignment film that covers the second electrodeand is subjected to an aligning treatment in a second direction crossingthe first direction at an angle of substantially 90° being provided on asurface facing the first substrate; and a liquid crystal layer that istwist-aligned and held at a twisted angle of substantially 90° betweenthe first alignment film of the first substrate and the second alignmentfilm of the second substrate. It is preferable for the first polarizingplate has a first polarizing layer to have an absorption axis in adirection crossing an aligning treatment direction of the firstalignment film at an angle of substantially 45°, and for the secondpolarizing plate to have a second polarizing layer having an absorptionaxis in a direction substantially perpendicular to or substantiallyparallel to the absorption axis of the first polarizing layer.

In the liquid crystal display device according to the present invention,each of the first and second polarizing layers preferably includes abase film formed of a resin film that is provided on at least a surfaceof the polarizing layer facing the first or second substrate and has aretardation in a thickness direction, which is a product of a phasedifference within a plane perpendicular to the substrate surfaces and alayer thickness. Each of the first and second viewing angle compensatinglayers preferably includes a base film formed of a resin film that isprovided on at least one surface of the viewing angle compensating layerand has a retardation in the thickness direction, which is a product ofa phase difference within a plane perpendicular to the substratesurfaces and a layer thickness. The plurality of optical layers betweenthe first and second polarizing layers excluding the liquid crystallayer preferably include at least the base films on the surfaces of thefirst and second polarizing layers facing the first and secondsubstrates, the first and second viewing angle compensating layers, andthe base films of these viewing angle compensating layers.

In the liquid crystal display device according to the present invention,it is preferable that a first retardation plate is further arrangedbetween the first polarizing layer and the first viewing anglecompensating layer and a second retardation plate is further arrangedbetween the second polarizing layer and the second viewing anglecompensating layer. In this case, each of the first and secondpolarizing layers preferably includes a base film formed of a resin filmthat is provided on at least the surface of the polarizing layer facingthe first or second substrate and has a retardation in the thicknessdirection, which is a product of a phase difference within a planeperpendicular to the substrate surfaces and a layer thickness, and thefirst and second viewing angle compensating layers are preferablyrespectively formed on plate surfaces of the first retardation plate andthe second retardation plate. Furthermore, each of the first and secondpolarizing layers preferably includes a base film formed of a resin filmarranged on an outer surface of the polarizing layer opposite to thesurface facing the first or second substrate. Each of the first andsecond viewing angle compensating layers preferably includes a base filmformed of a resin film that is provided on at least one surface of theviewing angle compensating layer and has a retardation in the thicknessdirection, which is a product of a phase difference in a planeperpendicular to the substrate surfaces and a layer thickness. The firstand second retardation plates are preferably laminated on the surfacesof the first and second polarizing layers facing the first and secondsubstrates, respectively. Moreover, each of the first and secondpolarizing layers preferably includes a base film formed of a resin filmarranged on the outer surface of the polarizing layer opposite to thesurface facing the first or second substrate. The first and secondretardation plates are preferably laminated on the surfaces of the firstand second polarizing layers facing the first and second substrates,respectively. The first and second viewing angle compensating layers arepreferably formed on the plate surfaces of the first and secondretardation plates, respectively. Additionally, it is preferable that anoptical film is further arranged either between the first retardationplate and the first viewing angle compensating layer or between thesecond retardation plate and the second viewing angle compensatinglayer, the optical film having one refractive index nx and the otherrefractive index in two directions perpendicular to each other within aplane parallel to the substrate surfaces, aid a refractive index nz in athickness direction perpendicular to the substrate surfaces satisfying arelationship of nx=ny>nz.

The liquid crystal display device according to the present inventionincludes: a first substrate having at least one electrode and a firstalignment film that covers the first electrode and is subjected to analigning treatment in a predetermined first direction being provided onone surface thereof; a second substrate having at least one secondelectrode that faces the first electrode and a second alignment filmthat covers the second electrode and is subjected to an aligningtreatment in a second direction that crosses the first direction at anangle of substantially 90° being provided on a surface facing the firstsubstrate; a liquid crystal layer that is sandwiched between the firstalignment film of the first substrate and the second alignment film ofthe second substrate and includes liquid crystal molecules twist-alignedat a twisted angle of substantially 90° between the first alignment filmand the second alignment film; a first polarizing plate including afirst polarizing layer that is arranged to face an outer surfaceopposite to an electrode formation surface of the first electrode andhas an absorption axis in a direction crossing the aligning treatmentdirection of the first alignment film at an angle of substantially 45°,and a base film formed of a resin film that is provided on a surface ofthe first polarizing layer facing the first substrate and has aretardation in a thickness direction, which is a product of a phasedifference within a plane perpendicular to substrate surfaces of thefirst and second substrates and a layer thickness; a second polarizingplate including a second polarizing layer that is arranged to face anouter surface opposite to an electrode formation surface of the secondsubstrate and has an absorption axis in a direction substantiallyperpendicular to or substantially parallel to the absorption axis of thefirst polarizing layer, and a base film formed of a resin film that isprovided on a surface of the second polarizing layer facing at least thesecond substrate and has a retardation in a thickness direction, whichis a product of a phase difference within a plane perpendicular to thesubstrate surfaces and a layer thickness; and first and second viewingangle compensating plates that are respectively arranged between thefirst substrate and the first polarizing plate and between the secondsubstrate and the second polarizing plate and each of which includes aviewing angle compensating layer having a phase difference within aplane parallel to the substrate surfaces and a phase difference within aplane perpendicular to the substrate surfaces, and a base film formed ofa resin film that is provided on at least one surface of the viewingangle compensating layer and has a retardation in a thickness direction,which is a product of a phase difference within the plane perpendicularto the substrate surfaces and a layer thickness. A total value of theretardation values in the thickness direction, each of which is aproduct of a phase difference within a plane perpendicular to thesubstrate surfaces and a layer thickness, of a plurality of opticallayers between the first polarizing layer of the first polarizing plateand the second polarizing layer of the second polarizing plate, theplurality of optical layers including the base films on the surfaces ofat least the first and second polarizing plates facing the first andsecond substrates between the first polarizing layer of the firstpolarizing plate and the second polarizing layer of the secondpolarizing plate, the respective viewing angle compensating layers ofthe first and second viewing angle compensating plates, and the basefilms of the first and second viewing angle compensating plates butexcluding the liquid crystal layer, and a retardation value in a liquidcrystal layer thickness direction, which is a product of a phasedifference within a plane perpendicular to the substrate surfaces and aliquid crystal layer thickness, of the liquid crystal layer when avoltage sufficiently high to raise and align the liquid crystalmolecules with respect to the substrate surfaces is applied to theliquid crystal layer between the electrodes of the first and secondsubstrates is set to the range of −80 nm to +80 nm.

In this liquid crystal display device, it is preferable for theretardation in the liquid crystal layer thickness direction to be avalue calculated by multiplying a value of a product Δnd of ananisotropic refractive index Δn of a liquid crystal materialconstituting the liquid crystal layer and a liquid crystal layerthickness d by a coefficient in the range of 0.72 to 0.89 selected inaccordance with a pre-tilt angle of the liquid crystal molecules withrespect to the substrate surfaces and a value of the voltagesufficiently high to raise and align the liquid crystal molecules.

Furthermore, it is preferable for a total value of in-plane retardationsof the plurality of optical layers between the first and secondpolarizing layers, including the plurality of base films, the pluralityof viewing angle compensating layers, and the liquid crystal layer, tobe set to the range of 350 nm to 600 nm, the in-plane retardation beinga product of an in-plane phase difference within a plane parallel to thesubstrate surfaces and a layer thickness of each of the plurality ofoptical layers.

Moreover, it is preferable for a first retardation plate to be arrangedbetween the first polarizing layer and the first viewing anglecompensating layer and a second retardation plate to be arranged betweenthe second polarizing layer an the second viewing angle compensatinglayer.

The liquid crystal display device according to the present inventionincludes: a first substrate having at least one first electrode and afirst alignment film that covers the first electrode and is subjected toan aligning treatment in a predetermined first direction being providedon one surface thereof; a second substrate that is arranged to face anelectrode formation surface of the first electrode and has at least onesecond electrode that faces the first electrode and a second alignmentfilm that covers the second electrode and is subjected to an aligningtreatment in a second direction crossing the first direction at an angleof substantially 90° being provided on a surface facing the firstsubstrate; a liquid crystal layer that is sandwiched between the firstalignment film of the first substrate and the second alignment film ofthe second substrate and includes liquid crystal molecules twist-alignedat a twisted angle of substantially 90° between the first alignment filmand the second alignment film; a first polarizing layer that is arrangedto face an outer surface opposite to the electrode formation surface ofthe first substrate and has an absorption axis in a direction crossingan aligning treatment direction of the first alignment film at an angleof substantially 45°; a second polarizing layer that is arranged to facean outer surface opposite to an electrode formation surface of thesecond substrate and has an absorption axis in a direction substantiallyperpendicular to or parallel to the absorption axis of the firstpolarizing layer; and first and second viewing angle compensating layersthat are respectively arranged between the first polarizing layer of thefirst substrate and the second polarizing layer of the second substrateand each of which has a phase difference within a plane parallel tosubstrate surfaces of the first and second substrates and a phasedifference within a plane perpendicular to the substrate surfaces. Inregard to each of a plurality of optical layers between the first andsecond polarizing layers including at least the first and second viewingangle compensating layers but excluding the liquid crystal layer,assuming that one and the other of two directions perpendicular to eachother within a plane parallel to the substrate surfaces are an X axisand a Y axis, a thickness direction perpendicular to the substratesurfaces is a Z axis, a refractive index in the X axis direction is nx,a refractive index in the Y axis direction is ny, a refractive index inthe Z axis direction is nz, a layer thickness of the optical layer is d,a retardation in the thickness direction of each optical layerrepresented as {(nx+ny)/2−nz}·d is Rthi, a retardation in the thicknessdirection obtained by adding the values of the retardations Rthi in thethickness direction of the respective optical layers is Rth, and aproduct of an anisotropic refractive index Δn of a liquid crystalmaterial constituting the liquid crystal layer and a liquid crystallayer thickness d is Δnd, the retardation Rth in the thickness directionis set to the range satisfying −80 nm<Rth-0.83 Δnd<80 nm

In this liquid crystal display device, in regard to the plurality ofoptical layers between the first polarizing layer and the secondpolarizing layer, assuming that an in-plane retardation of each opticallayer represented as (nx−ny)·d is Roi, and an in-plane retardationobtained by adding values of the in-plane retardations of the respectiveoptical layers is Ro, it is preferable for each of the in-planeretardation Ro and Δnd of the liquid crystal layer to be set to therange satisfying Ro+Δnd=350 nm to 600 nm.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A liquid crystal display device comprising: first and secondpolarizing layers which are arranged so that their transmission axes areperpendicular to each other; a liquid crystal cell arranged between thefirst and second polarizing layers; a first viewing angle compensatingplate arranged between the first polarizing layer and the liquid crystalcell; a second viewing angle compensating plate arranged between thesecond polarizing layer and the liquid crystal cell; a first base filmwhich is arranged between the first polarizing layer and the firstviewing angle compensating plate, and which supports the firstpolarizing layer; and a second base film which is arranged between thesecond polarizing layer and the second viewing angle compensating plate,and which supports the second polarizing layer, wherein the liquidcrystal cell includes: a first substrate on which a first electrode isformed; a second substrate on which a second electrode is formed; and aliquid crystal layer that (i) is arranged between the first electrodeand the second electrode and comprises liquid crystal that has apositive dielectric anisotropy, (ii) is twist-aligned at a twisted angleof 90° when voltage is not applied between the first and secondelectrodes, and (iii) causes a retardation to remain in a plane parallelto a substrate surface when a predetermined saturation voltage isapplied between the first and second electrodes, wherein the secondviewing angle compensating plate includes a compensating layercomprising a hybrid-aligned discotic liquid crystal, wherein a tiltdirection of the discotic liquid crystal provided as an optical axis isset parallel to a direction of molecule orientation at the firstsubstrate side in the liquid crystal layer when a voltage is not appliedbetween the first and second electrodes, and wherein a total value ofretardations in a plane perpendicular to the substrate surface ofoptical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 2. The liquid crystal display device according toclaim 1, wherein the first and second viewing angle compensating platescompensate the retardation in the plane parallel to the substratesurface that remains in the liquid crystal layer when the saturationvoltage is applied.
 3. The liquid crystal display device according toclaim 1, wherein a bisector of the twisted angle of the liquid crystallayer when voltage is not applied between the first and secondelectrodes is set parallel to a transmission axis of the firstpolarizing layer or a transmission axis of the second polarizing layer.4. The liquid crystal display device according to claim 1, furthercomprising a first retardation plate arranged between the first basefilm and the first viewing angle compensating plate.
 5. The liquidcrystal display device according to claim 4, further comprising a secondretardation plate arranged between the second base film and the secondviewing angle compensating plate.
 6. The liquid crystal display deviceaccording to claim 1, wherein the liquid crystal layer has a pre-tiltangle.
 7. A liquid crystal display device comprising: first and secondpolarizing layers which are arranged so that their transmission axes areperpendicular to each other; a liquid crystal cell arranged between thefirst and second polarizing layers; a first viewing angle compensatingplate arranged between the first polarizing layer and the liquid crystalcell; a second viewing angle compensating plate arranged between thesecond polarizing layer and the liquid crystal cell; a first base filmwhich is arranged between the first polarizing layer and the firstviewing angle compensating plate, and which supports the firstpolarizing layer; and a second base film which is arranged between thesecond polarizing layer and the second viewing angle compensating plate,and which supports the second polarizing layer, wherein the liquidcrystal cell includes: a first substrate on which a first electrode isformed; a second substrate on which a second electrode is formed; and aliquid crystal layer that (i) is arranged between the first electrodeand the second electrode and comprises liquid crystal that has apositive dielectric anisotropy, (ii) is twist-aligned at a twisted angleof 90° when voltage is not applied between the first and secondelectrodes, and (iii) causes a retardation to remain in a plane parallelto a substrate surface when a predetermined saturation voltage isapplied between the first and second electrodes, wherein the firstviewing angle compensating plate includes a compensating layercomprising a hybrid-aligned discotic liquid crystal, wherein a tiltdirection of the discotic liquid crystal provided as an optical axis isset parallel to a direction of molecule orientation at the secondsubstrate side in the liquid crystal layer when a voltage is not appliedbetween the first and second electrodes, and wherein a total value ofretardations in a plane perpendicular to the substrate surface ofoptical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 8. The liquid crystal display device according toclaim 7, wherein the first and second viewing angle compensating platescompensate the retardation in the plane parallel to the substratesurface that remains in the liquid crystal layer when the saturationvoltage is applied.
 9. The liquid crystal display device according toclaim 7, wherein a bisector of the twisted angle of the liquid crystallayer when voltage is not applied between the first and secondelectrodes is set parallel to a transmission axis of the firstpolarizing layer or a transmission axis of the second polarizing layer.10. The liquid crystal display device according to claim 7, furthercomprising a first retardation plate arranged between the first basefilm and the first viewing angle compensating plate.
 11. The liquidcrystal display device according to claim 10, further comprising asecond retardation plate arranged between the second base film and thesecond viewing angle compensating plate.
 12. A liquid crystal displaydevice comprising: first and second polarizing layers which are arrangedso that their transmission axes are perpendicular to each other; aliquid crystal cell arranged between the first and second polarizinglayers; a first viewing angle compensating plate arranged between thefirst polarizing layer and the liquid crystal cell; a second viewingangle compensating plate arranged between the second polarizing layerand the liquid crystal cell; a first base film which is arranged betweenthe first polarizing layer and the first viewing angle compensatingplate, and which supports the first polarizing layer; and a second basefilm which is arranged between the second polarizing layer and thesecond viewing angle compensating plate, and which supports the secondpolarizing layer, wherein the liquid crystal cell includes: a firstsubstrate on which a first electrode is formed; a second substrate onwhich a second electrode is formed; and a liquid crystal layer that (i)is arranged between the first electrode and the second electrode andcomprises liquid crystal that has a positive dielectric anisotropy, (ii)is twist-aligned at a twisted angle of 90° when voltage is not appliedbetween the first and second electrodes, and (iii) causes a retardationto remain in a plane parallel to a substrate surface when apredetermined saturation voltage is applied between the first and secondelectrodes, wherein the liquid crystal display device further comprisesa first optical film arranged between a first retardation plate and thefirst viewing angle compensating plate, the first optical film having arefractive index in the plane parallel to the substrate surface that isuniform in any direction and a refractive index in a substrate thicknessdirection that is different from the refractive index in the planeparallel to the substrate surface, and wherein a total value ofretardations in a plane perpendicular to the substrate surface ofoptical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 13. The liquid crystal display device accordingto claim 12, wherein the first and second viewing angle compensatingplates compensate the retardation in the plane parallel to the substratesurface that remains in the liquid crystal layer when the saturationvoltage is applied.
 14. The liquid crystal display device according toclaim 12, wherein a bisector of the twisted angle of the liquid crystallayer when voltage is not applied between the first and secondelectrodes is set parallel to a transmission axis of the firstpolarizing layer or a transmission axis of the second polarizing layer.15. The liquid crystal display device according to claim 12, furthercomprising a first retardation plate arranged between the first basefilm and the first viewing angle compensating plate.
 16. The liquidcrystal display device according to claim 15, further comprising asecond retardation plate arranged between the second base film and thesecond viewing angle compensating plate.
 17. A liquid crystal displaydevice comprising: first and second polarizing layers which are arrangedso that their transmission axes are perpendicular to each other; aliquid crystal cell arranged between the first and second polarizinglayers; a first viewing angle compensating plate arranged between thefirst polarizing layer and the liquid crystal cell; a second viewingangle compensating plate arranged between the second polarizing layerand the liquid crystal cell; a first base film which is arranged betweenthe first polarizing layer and the first viewing angle compensatingplate, and which supports the first polarizing layer; and a second basefilm which is arranged between the second polarizing layer and thesecond viewing angle compensating plate, and which supports the secondpolarizing layer, wherein the liquid crystal cell includes: a firstsubstrate on which a first electrode is formed; a second substrate onwhich a second electrode is formed; and a liquid crystal layer that (i)is arranged between the first electrode and the second electrode andcomprises liquid crystal that has a positive dielectric anisotropy, (ii)is twist-aligned at a twisted angle of 90° when voltage is not appliedbetween the first and second electrodes, and (iii) causes a retardationto remain in a plane parallel to a substrate surface when apredetermined saturation voltage is applied between the first and secondelectrodes, wherein the liquid crystal display device further comprisesa first optical film arranged between a first retardation plate and thefirst viewing angle compensating plate, the first optical film having arefractive index in the plane parallel to the substrate surface that isuniform in any direction and a refractive index in a substrate thicknessdirection that is different from the refractive index in the planeparallel to the substrate surface, and wherein a total value ofretardations in a plane perpendicular to the substrate surface ofoptical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 18. The liquid crystal display device accordingto claim 17, further comprising a second optical film arranged between asecond retardation plate and the second viewing angle compensatingplate, the second optical film having a refractive index in the planeparallel to the substrate surface that is uniform in any direction and arefractive index in a substrate thickness direction that is differentfrom the refractive index in the plane parallel to the substratesurface.
 19. A liquid crystal display device comprising: first andsecond polarizing layers which are arranged so that their transmissionaxes are perpendicular to each other; a liquid crystal cell arrangedbetween the first and second polarizing layers; a first viewing anglecompensating plate arranged between the first polarizing layer and theliquid crystal cell; a second viewing angle compensating plate arrangedbetween the second polarizing layer and the liquid crystal cell; a firstbase film which is arranged between the first polarizing layer and thefirst viewing angle compensating plate, and which supports the firstpolarizing layer; and a second base film which is arranged between thesecond polarizing layer and the second viewing angle compensating plate,and which supports the second polarizing layer, wherein the liquidcrystal cell includes: a first substrate on which a first electrode isformed; a second substrate on which a second electrode is formed; and aliquid crystal layer that (i) is arranged between the first electrodeand the second electrode and comprises liquid crystal that has apositive dielectric anisotropy, (ii) is twist-aligned at a twisted angleof 90° when voltage is not applied between the first and secondelectrodes, and (iii) causes a retardation to remain in a plane parallelto a substrate surface when a predetermined saturation voltage isapplied between the first and second electrodes, wherein the liquidcrystal cell includes: a pixel on which a color filter of a redcomponent is formed; a pixel on which a color filter of a greencomponent is formed; and a pixel on which a color filter of a bluecomponent is formed, wherein a thickness of the liquid crystal layer isdifferent among each of the pixels, and wherein a total value ofretardations in a plane perpendicular to the substrate surface ofoptical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 20. The liquid crystal display device accordingto claim 19, wherein Δnd of the liquid crystal layer at each of thepixels is equal at λ/2, where λ is a wavelength of a color componentcorresponding to each of the pixels.
 21. The liquid crystal displaydevice according to claim 19, wherein the liquid crystal layer istwist-aligned clockwise with respect to a direction in which lightproceeds.
 22. A liquid crystal display device comprising: first andsecond polarizing layers which are arranged so that their transmissionaxes are perpendicular to each other; a liquid crystal cell arrangedbetween the first and second polarizing layers; a first viewing anglecompensating plate arranged between the first polarizing layer and theliquid crystal cell; a second viewing angle compensating plate arrangedbetween the second polarizing layer and the liquid crystal cell; a firstbase film which is arranged between the first polarizing layer and thefirst viewing angle compensating plate, and which supports the firstpolarizing layer; and a second base film which is arranged between thesecond polarizing layer and the second viewing angle compensating plate,and which supports the second polarizing layer, wherein the liquidcrystal cell includes: a first substrate on which a first electrode isformed; a second substrate on which a second electrode is formed; and aliquid crystal layer that (i) is arranged between the first electrodeand the second electrode and comprises liquid crystal that has apositive dielectric anisotropy, (ii) is twist-aligned at a twisted angleof 90° when voltage is not applied between the first and secondelectrodes, and (iii) causes a retardation to remain in a plane parallelto a substrate surface when a predetermined saturation voltage isapplied between the first and second electrodes, wherein the first andsecond base films are formed of triacetylcellulose, and wherein a totalvalue of retardations in a plane perpendicular to the substrate surfaceof optical layers arranged between the first polarizing layer and theliquid crystal cell and optical layers arranged between the secondpolarizing layer and the liquid crystal cell is set to a value that hasan opposite sign to and the same absolute value as a retardation valuein the plane perpendicular to the substrate surface of the liquidcrystal layer when the saturation voltage is applied between the firstand second electrodes.
 23. A liquid crystal display device comprising:first and second polarizing layers which are arranged so that theirtransmission axes are perpendicular to each other; a liquid crystal cellarranged between the first and second polarizing layers; a first viewingangle compensating plate arranged between the first polarizing layer andthe liquid crystal cell; a second viewing angle compensating platearranged between the second polarizing layer and the liquid crystalcell; a first base film which is arranged between the first polarizinglayer and the first viewing angle compensating plate, and which supportsthe first polarizing layer; and a second base film which is arrangedbetween the second polarizing layer and the second viewing anglecompensating plate, and which supports the second polarizing layer,wherein the liquid crystal cell includes: a first substrate on which afirst electrode is formed; a second substrate on which a secondelectrode is formed; and a liquid crystal layer that (i) is arrangedbetween the first electrode and the second electrode and comprisesliquid crystal that has a positive dielectric anisotropy, (ii) istwist-aligned at a twisted angle of 90° when voltage is not appliedbetween the first and second electrodes, and (iii) causes a retardationto remain in a plane parallel to a substrate surface when apredetermined saturation voltage is applied between the first and secondelectrodes, wherein the first viewing angle compensating plate includesa compensating layer comprising hybrid-aligned discotic liquid crystal,and a base film formed of triacetylcellulose supporting the compensatinglayer, and wherein a total value of retardations in a planeperpendicular to the substrate surface of optical layers arrangedbetween the first polarizing layer and the liquid crystal cell andoptical layers arranged between the second polarizing layer and theliquid crystal cell is set to a value that has an opposite sign to andthe same absolute value as a retardation value in the planeperpendicular to the substrate surface of the liquid crystal layer whenthe saturation voltage is applied between the first and secondelectrodes.
 24. The liquid crystal display device according to claim 23,wherein the second viewing angle compensating plate includes acompensating layer comprising hybrid-aligned discotic liquid crystal,and a base film formed of triacetylcellulose supporting the compensatinglayer.